The invention is a rotary tensioner for a safety belt, in particular in motor vehicles, with a belt retractor, the belt retraction spool of which is rotated in the belt retracting direction by an associated drive when the rotary tensioner coupled thereto is actuated, whereby the drive comprises a drive wheel that has exterior teeth for the spool, and a channel that extends about at least a portion of the periphery of the drive wheel for conducting therethrough inertia elements that are accelerated in the channel when the system is triggered and that engage the exterior teeth of the drive wheel.
DE 195 12 660 A1 describes a rotary tensioner with the aforesaid features, addressing the problem that when the first inertia element reaches the exterior teeth of the drive wheel, the passage of the subsequent inertia elements can be blocked by the drive wheel, or there can at least be interference in the proper functioning of the drive process. The solution provided for this in the generic document is inadequate, namely adjusting a resilience or elasticity of the components in question in the region in which the inertia elements and drive wheel meet one another in order to prevent mutual blocking of inertia elements and drive wheel due to a possible shifting in components designed in this manner.
The object of the invention is therefore to assure in a generic rotary tensioner that the inertia elements run across the drive wheel undisturbed with form-fit engagement of the inertia elements in its exterior teeth.
This object is achieved, including advantageous further developments of the invention, from the contents of the patent claims that follow this specification.
The basic idea of the invention is that a shaped element, comprising an inertia element and a leading finder element, is provided for the synchronous, shape-congruent introduction of the inertia elements into the exterior teeth of the drive wheel. In a simple manner and without substantial constructive complexity, this synchronizes the arrival of successive inertia elements and the position of the drive wheel, and of its exterior teeth, in that when the position of the exterior teeth of the drive wheel is not synchronous with the first incoming inertia element, the leading finder element corrects the position of the drive wheel, and of the affected recess of the exterior teeth, so that each of the subsequent inertia elements achieves an undisturbed form-fit with the exterior teeth of the drive wheel.
In a first embodiment, the invention provides that the shaped element comprises as finder element a first inertia element having only a partial contour of a complete inertia element adapted to the external teeth of the drive wheel, and also comprises a complete second inertia element integrally joined thereto via a connecting rib. This solution is based on the principle that due to the only partial contour of the first inertia element in the framework of the shaped element, the first inertia element as finder can enter into this recess until it is adjacent to the surface of the recess affected by the partial contour in the drive direction, independent of the position of the associated recess of the exterior teeth of the drive wheel, and thus if necessary corrects the position of the drive wheel so that the second inertia element, which is integrally joined to the first inertia element as a component of the shaped element and which thus is fixed in its association to the first inertia element, enters into the recess associated with it in a synchronized manner. This also ensures the passage of the further inertia elements following the second inertia element.
In terms of the embodiment of a double sphere comprising two inertia elements joined to one another, known from DE 196 02 549 A1, for achieving a sealing effect with an arrangement provided with a seal, this is located on the end allocated to the pyrotechnic drive, alternatively also on the other end, but the succession of inertia elements has no effect on the passage of the inertia elements through the exterior teeth of the drive wheel, which passage is to be improved.
The partial contour of the first inertia element in the framework of the shaped element is formed in accordance with one exemplary embodiment of the invention in that the partial contour of the first inertia element comprises a hemisphere oriented in the drive direction, whose terminating plane facing the second inertia element is arranged at an angle to the radius line of the drive wheel. This makes it possible for the first inertia element to fit the critical tooth of the exterior teeth of the drive wheel. When the following tooth is encountered, which theoretically is also located in a critical position, no blockage occurs because in this case the collision leads to a beginning rotary of the drive wheel due to the orientation of the tooth, changed by one tooth division, relative to the incoming inertia element.
In accordance with one exemplary embodiment of the invention, it is provided that the connecting rib at least partially continues the missing contour of the first inertia element to the second inertia element; this improves the orientation of the shaped element, i.e. the first inertia element relative to the teeth.
Known in the prior art is separating the drive wheel into two symmetrical halves; in accordance with one exemplary embodiment of the invention it is provided that the connecting rib engages between the halves of the drive wheel and the shaped element is guided thereby.
In a second exemplary embodiment of the invention it is provided that the finder element of the shaped element is embodied as a flat component that can be guided between the exterior edge of the drive wheel and the interior wall of the channel, and the drive wheel has formed on its exterior rim as control teeth a second set of teeth, whereby the exterior teeth, for receiving the inertia elements, and the control teeth, for cooperating with the finder component of the shaped element, are arranged relative to one another in such a way that the finder component, when there is a fitting association of the first inertia element that is attached to it to a recess of the exterior teeth, encounters the exterior contour of a tooth ridge located between the gaps of the control teeth and, during a critical association of inertia elements to the exterior teeth, engages a gap of the control teeth and rotates the drive wheel into the fitting position by pushing against the tooth flank.
This design is based on the principle that the finder is embodied as a finder component that cooperates with second control teeth formed on the drive wheel and that if necessary causes a correction in the position of the drive wheel. If the finder component encounters a tooth of the control teeth of the drive wheel, the control teeth are arranged relative to the exterior teeth of the drive wheel that receive the inertia elements such that the inertia element attached to the finder component enters the associated recess of the drive wheel synchronously; if the finder component encounters a gap of the control teeth, the position of the drive wheel is not synchronous to the entering inertia element, and in this case the finder component has a certain amount of play in the gap and due to abutment against the end of the gap in the drive direction of the drive wheel leads to a correction in position such that the exterior teeth of the drive wheel are synchronous to the entering inertia elements.
In accordance with one exemplary embodiment of the invention it is provided that the finder component is embodied as a T-shaped component with a T-piece that cooperates with the control teeth and is connected to the first inertia element, which is embodied as a sphere. In accordance with exemplary embodiments of the invention it can be provided that the finder component and the first inertia element are embodied integrally with one another, or that the finder component is spread open at its free end opposing the T-piece and thus engages the sphere in a form-fit in an associated groove. Preferably the T-shaped finder component can be embodied as a solid metal part.
In addition, for both embodiments of the invention it can be provided that the shaped element is fixed in its starting position by a clip fixed in the wall of the tubular housing that forms the channel; this is associated with the advantage that the inertia element is secured in its rest state via the shaped element joined to the clip; at the same time the clip makes it possible to align the shaped element with regard to the orientation of its longitudinal axis and with regard to a rotational orientation in the channel of the tubular housing. If the clip has a spring pre-tensioning or is plastically deformable due to its configuration, the clip additionally ensures a movement of the shaped element via the drive wheel to the extent that the shaped element can shift by a certain amount between the channel and the drive wheel, as is in particular necessary for the embodiment of the invention with the T-shaped finder component.
In accordance with one exemplary embodiment of the invention, the clip is advantageously fixed in the wall of the tubular housing by means of a shear pin.
In accordance with one exemplary embodiment of the invention it can be provided that the clip has a spring arm engaging between two inertia elements and pressing the series of successive inertia elements together, whereby the chain of inertia elements is pressed with no play against the securely clamping piston on the other end of the chain of inertia elements and the system is thereby prevented from chattering.